1. Field of the Invention
The present invention relates to a process for the treatment of glass in order to improve the adhesion of a polymer to the glass.
2. Discussion of the Background
Different solutions making it possible to improve the adhesion of polymers to glass have been described in the prior art. The problem encountered by many of these solutions is that glass-polymer adhesion is not obtained in a satisfactory manner.
French patent 2,519,956 describes a process consisting of depositing on the lip of a hollow glass object, a coating of tin oxide, onto which is then deposited a chromium complex in order to ensure a stronger bond between glass and polymer. This procedure offers satisfactory results, but requires very difficult conditions with respect to the deposition of the chromium complex, due to instability of the chromium complex.
The process requires precise control of the pH and temperature of the chromium complex solution in order to provide good durability of the complex.
French patent application No. FR 9,304,329 discloses a glass treatment which also requires difficult conditions. It proposes a two-stage treatment consisting of the deposition of a metal oxide coating and the deposition of a coating of a soluble chromium salt, such as chromium nitrate. While the heat sealing results obtained with this treatment are completely satisfactory, again the treatment is extremely difficult to perform satisfactorily.
Certain applications requiring a very high temperature, particularly for decoration, cannot be coated with a chromium-based solution, which is proscribed at very high temperatures.
European patent 158,830 describes another type of treatment for glass containers which are to be ultimately heat sealed. EP 158,830 provides a process consisting of depositing a composition containing at least one resin amide or acrylic bond. However, the heat sealing results obtained with this process are not always satisfactory.